Chyýlek P, Srivastava V, Pinnick R G, Wang R T
Appl Opt. 1988 Jun 15;27(12):2396-404. doi: 10.1364/AO.27.002396.
We have measured the differential scattering cross sections (phase functions I(22)) and the normalized extinction and scattering cross sections (efficiences) of composite spherical particles. The size parameter x = 2pir/lambda was around 2pi. Composite spheres consisted of nonabsorbing matrix containing a small amount (1.6 and 2.7% by volume) of highly absorbing inclusions. Such composite particles may represent a realistic model of fog or cloud droplets containing small amounts of carbon or a composite atmospheric aerosol particle. We have compared measured data with those calculated using seven different effective medium approximations. We have found that the approximations of Bruggeman and Maxwell Garnett, the generalization of dynamic effective medium approximation derived by Chylek and Srivastava, and the experimental waveguide method of determination of the effective refractive index lead to an acceptable agreement between calculated and measured values. The reduced x(2) values for these approximations ranged between 0.6 and 2.0. The remaining three approximations (volume averages of refractive indices or dielectric constants and the Maxwell Garnett relation with matrix and inclusion materials interchanged) lead to reduced x(2) values between 4.0 and 12.0 demonstrating characteristics.
我们测量了复合球形颗粒的微分散射截面（相位函数I(22)）以及归一化消光截面和散射截面（效率）。尺寸参数x = 2πr/λ约为2π。复合球体由含有少量（体积分数为1.6%和2.7%）高吸收性内含物的非吸收性基质组成。这种复合颗粒可能代表了含有少量碳的雾或云滴的实际模型，或者是一种复合大气气溶胶颗粒。我们将测量数据与使用七种不同有效介质近似方法计算得到的数据进行了比较。我们发现，布鲁格曼近似和麦克斯韦-加内特近似、奇莱克和斯里瓦斯塔瓦推导的动态有效介质近似的推广，以及确定有效折射率的实验波导方法，使得计算值与测量值之间达成了可接受的一致性。这些近似方法的约化χ²值在0.6到2.0之间。其余三种近似方法（折射率或介电常数的体积平均以及基质和内含物材料互换后的麦克斯韦-加内特关系）导致约化χ²值在4.0到12.0之间，呈现出不同的特征。
